1. Field of the Invention
The invention relates to a closeable container, especially a glass bottle or glass inlet, comprising a plastic coating applied by injection molding and also to an injection molding method of applying it.
2. Description of the Related Art
Glass containers of this type comprising a coating applied by injection molding are used for medical purposes in particular, but they are also used for cosmetic purposes or to store food and beverages. The purpose of these plastic coatings, for example, is to hold glass splinters together if the coated glass container breaks. The plastic coating therefore also serves to provide protection against bursting and/or shattering.
Glass containers of various species comprising a plastic coating applied in different fashions using the most diverse types of plastics have been made known in numerous publications.
In DE-OS 24 31 952 it was made known to coat glass bottles with a plastic that comprises a thermosetting resin that is softened before use, either by means of internal plasticizers, i.e., by means of substances that react during production of the thermosetting plastic and thereby become part of the resin, or by means of external plasticizers that are added to the finished resin in suitable fashion. The softened, thermosetting resin is available as coating powder, is ground to a specified particle size, and then applied electrostatically to the bottles. The application of the powder can also take place by means of immersion in a fluidized bed or in an electrostatic fluidized bed. The applied layer is then cured, preferably in an infrared oven. In this known case, the coating of the bottles therefore takes place using the method of powder coating on a thermosetting basis. This method does not permit exact shaping of the coated bottle, as required, for example, to shape the base section with regard for the stability of the glass bottle, and is also relatively costly.
Furthermore, the softened thermosetting resin cannot be applied to the glass bottles using the technique of injection molding, because this technique requires that a plastic molding compound be available that can be softened under the influence of heat, so that it can then be pressed into the molding die. By definition, thermosetting plastics are not capable of being heat-softened, however.
To the extent that glass containers have been put into concrete terms in the publications about the related art, containers such as beer bottles, mineral water bottles, cosmetic containers and the like are typically named. Additionally, the principles of coating glass containers by injection molding are also used with a special species of containers, namely closeable medical containers subject to a relatively high pressure. These pressurizable medical containers can be filled under pressure with medically effective substances and a propellant. These containers have an opening which is closeable using a delivery element, in particular a metering valve. A dispensing head is provided that interacts with the delivery element in such a fashion that the delivery element is actuated when both parts are pressed together. A certain quantity of the medically effective substance is then released through a spray opening as an aerosol. These products serve as applicators for medical applications, in particular for patients with asthma or other bronchopathies.
The use of pressure containers made of metallic materials for such applicators is known. The protection against bursting and/or shattering in pressure containers of this type is achieved by means of the properties of the selected material that are advantageous in this regard (high toughness, high strength).
A disadvantage of these metallic pressure containers, however, is that the nontransparent pressure container makes it impossible to visually determine how much of the substance to be released remains inside. This is a particular disadvantage when it comes to dispensing inhalants that often have the character of an emergency remedy (e.g., asthma preparations). Without a visual check, the risk exists that the pressure container could be empty when an emergency arises.
Additionally, a pressure container in the form of a small glass bottle was made known in DE-AS 11 08 383. The capacity of the small glass bottle can be 5 to 50 ml. The release opening is located on the top end of the bottle. This is usually closed by inserting the delivery element, e.g., a metering valve having a usually cylindrical cannula projecting upward, into the pressure container or crimping it on the pressure container, often using an elastic seal between head and metering valve. The pressure container is thereby subjected to a relatively high internal pressure.
The known pressure container made of glass is covered with a coating of a transparent plastic that is sprayed on or applied via immersion, with the exception of the rim, to which the metering valve is crimped. This coating comprises a flexible soft plastic, e.g., PVC, having a great ability to stretch or expand. The great expandability is important, because, if the glass container bursts, the high internal pressure acts on the soft plastic. If the soft plastic of the coating could not yield to the high pressure by deformation, e.g., by a volume change of the coating jacket, a sudden destruction of the soft plastic resulting from chemical attack would be expected.
Since the pressure container is comprised of a transparent material (glass) and the plastic sheathing is transparent, this known pressure container has the advantage that it makes it possible to visually determine how much of the substance to be released remains inside.
A disadvantage of the known pressure container, however, is the fact that the transparent pressure container made of glass—despite its plastic coating—is not safe enough in case of explosion, e.g., caused by improper handling, because a coating is not applied in the region of the metering valve, or because, generally speaking, if bursting occurs, the plastic sheathing can expand and burst like a balloon, which causes parts of the glass container to spray rapidly into the surroundings, including the metering valve in particular, which can come loose from the rim to which it was crimped.
During the production of the final pressure container, the plastic layer that provides protection against bursting and shattering is applied directly to the glass pressure container in the simplest fashion possible—i.e., not by means of immersion or spraying—by coating this with an extruded plastic in a molding die. A concept of this type was made known in FR 2 631 581 B1. This publication describes a small glass bottle having a tapered neck section that can be filled under pressure with a substance sprayable as aerosol and a propellant, the opening of which is closeable using a delivery element, and that comprises a plastic coating applied by injection molding.
In the known case, the glass pressure container comprises a small bottle having a cylindrical neck section, and the molding die is designed so that a plastic coating is also applied by injection molding to the neck section flush with the opening of the small bottle. When the neck section of the small glass bottle is designed in this fashion, however, attachment of the delivery element—the metering valve—is not without problems. Furthermore, the plastic coating coats the small glass bottle completely. If bursting occurs, the coating can partly expand and burst and therefore lose its property of providing protection against bursting and shattering. The aforementioned publication furthermore makes no statement about the type of plastic material; it is therefore not considered to be essential in terms of function.
A further example of the aforementioned concept was made known in DE 196 32 664 A1. It discloses a small glass bottle having a tapered neck section that is fillable under pressure with a substance sprayable as aerosol and a propellant, the opening of which is closeable using a delivery element, that comprises a plastic coating applied by injection molding, and that is designed so that a secure attachment of the delivery element and a reduction of the wall thickness of the small glass bottle is possible and, on the other hand, the protection against bursting and shattering is increased considerably compared to the container made known in the FR publication. This known small bottle also comprises the following features:                the neck section comprises a sealing rim designed in the shape of a bead on the side where the opening is located for the mechanical attachment of the delivery element, which also comprises a plastic coating applied by injection molding,        a plurality of pressure-compensating openings designed in the shape of holes is formed in the plastic coating of the glass body applied by injection molding,        the coating is composed of an elastic plastic material having distinct shrinkage, and it is shrunk on the small glass bottle.        
Due to the sealing rim designed in the shape of a bead, a secure and permanent mechanical attachment of the delivery element is possible. Since the plastic coating also covers the glass sealing rim, the delivery element is still held mechanically even if the glass body bursts, which increases the protection against bursting. The pressure-compensating openings prevent the plastic coating from expanding and bursting, which also greatly increases the protection against bursting and shattering.
If bursting occurs, the filled substance and the propellant can escape through these pressure-compensating openings. Furthermore, due to the fact that the contents of the glass container can escape, the risk that the filled substance will chemically attack the coating material, e.g., by means of stress corrosion cracking, is further reduced, which further reduces the risk of bursting.
By using an elastic plastic material having distinct shrinkage, it was found that the ability of the small glass bottle coated by injection molding to be pressure-loaded is higher than the ability of the pure glass bottle to be pressure-loaded, by many times over. This effect makes a thinner wall thickness of the small glass bottle possible. The elasticity of the plastic material thereby offsets the shrinkage.
The present invention described hereinbelow is based on a glass container of this type.
In the known case, specially designed small glass bottles, “glass inlets”, are coated with a transparent plastic using the conventional injection-molding system. Since relatively viscous thermoplastics are typically used as plastic material in the conventional injection-molding system, very high injection pressures (approx. 300 bar) occur during injection molding, which can easily destroy the glass inlet. This destruction results in a high percentage of waste. Additionally, the productivity of a manufacturing system is greatly reduced. For this reason, limits are also placed on the reduction of the wall thickness of the glass inlets. The same applies for inlets made of a thermolabile plastic, especially a thermoplastic material.
Moreover, the known glass containers comprising a coating applied by injection molding cannot be sterilized by means of autoclaving using superheated steam at 121° C. for a period of 20 minutes. A sterilization method of this type is typically required for containers used for medical purposes, however.